Switching noise can affect the operation of a circuit, whether the circuit is an analog circuit, a digital circuit, or a mixed signal circuit. When transistors of a circuit switch from a conducting state to a non-conducting state, or from a non-conducting state to a conducting state, noise is generated in the circuit. The switching noise occurs when output from a power supply to the circuit varies based on changing power demands within the circuit. Switching noise is made worse by increasing the number of transistors switching simultaneously. Because many circuits have clock signals that synchronize operation of transistors across the circuit, switching noise may be worst around transitions in the clock signal, when transistors within the circuit switch from conducting to non-conducting or vice versa.
Switching noise can affect circuits constructed on a common substrate, because signals in the circuit are coupled to the substrate through the transistors that are constructed on the substrate. In a mixed signal system, analog and digital circuits may be built on a common substrate. Switching noise in the digital circuits of the mixed signal system may affect sampling of analog values in the analog circuits of the mixed signal system.
One conventional solution is to synchronize clock signals between a data clock and an internal clock used by the analog and digital circuits to reduce noise effects on analog data sampling. However, the synchronization results in a hard delay of at least a half cycle or one cycle of the internal clock. As a result of the hard delay, the performance of the circuit may suffer. Further, the additional circuitry for synchronizing the clock signals consumes die area on a substrate and consumes power, which further degrades performance of the circuit.